1. Field of the Invention
The present invention relates generally to a rotor for a torque sensor and, more particularly, to a rotor for a torque sensor, configured to improve a mechanical coupling force with respect to a jig in a process of adjusting a torque center, thus enabling a fine adjustment.
2. Description of the Related Art
Generally, a vehicle is configured to change a driving direction by manipulating a steering wheel connected to a wheel. However, if resistance between the wheel and a mad is large or there is an obstacle to steering, a manipulation force is decreased, thus making it difficult to rapidly manipulate. In order to solve the problem, a power steering system has been used. Such a power steering system includes a power unit to manipulate the steering wheel, thus reducing a manipulation force.
In order for the power unit to assist in manipulating the steering wheel, it is necessary to measure torque acting on a steering shaft. Thus, several types of devices are used to measure torque of the steering wheel. Among them, a device detecting torque by measuring a magnetic field relative to a magnet coupled to the steering shaft has been widely used because it is more economical.
A general steering structure includes an input shaft to which a steering wheel is coupled, an output shaft coupled to a pinion engaging with a rack bar of a wheel, and a torsion bar connecting the input shaft and the output shaft.
If the steering wheel rotates, a rotating force is transmitted to the output shaft, and the wheel changes its direction by interaction between the pinion and the rack bar. Here, the larger resistance is, the more the input shaft rotates. Hence, the torsion bar is twisted. A degree to which the torsion bar is twisted is measured by the torque sensor using the magnetic field.
When the steering wheel is not manipulated, the torque sensor maintains a central position. If a set center is erroneous, there occurs a difference in auxiliary steering force between left and right sides during a manipulation of the steering wheel. Thus, as for the power steering system, it is very important to adjust the center of the torque sensor.
FIG. 1 is a perspective view showing a conventional rotor for a torque sensor.
A rotor 1 having a magnet 2 is coupled to an input shaft of a steering system, and a stator (not shown) is coupled to an output shaft.
If the torsion bar is twisted by a difference in rotation amount between the input shaft coupled to the rotor 1 and the output shaft coupled to the stator, the magnet 2 and the stator rotate relative to each other. At this time, opposite surfaces between the magnet 2 and the stator are changed, so that a magnetization value is changed, and thereby torque may be measured using the change in magnetization value.
The rotor 1 includes a sleeve 4 coupled to an outer circumference of the input shaft, and a yoke 3 coupled with the sleeve 4 to allow the magnet 2 to be coupled to an outer circumference thereof.
In order to adjust the center of the torque sensor, there has been used a method of holding a predetermined portion on the outer circumference of the sleeve 4 by a jig and then rotating the rotor 1 by a frictional force.
However, such a method is problematic in that the jig rotates the outer circumference of the sleeve by the frictional force, so that there is a relatively strong possibility that the jig will slip from the sleeve, and it is difficult to finely adjust the center.